1. Field of the Invention
The present invention relates generally to photovoltaic devices. The present invention relates more particularly to photovoltaic roofing products in which photovoltaic elements are affixed to roofing substrates.
2. Summary of the Related Art
The search for alternative sources of energy has been motivated by at least two factors. First, fossil fuels have become increasingly expensive due to increasing scarcity and unrest in areas rich in petroleum deposits. Second, there exists overwhelming concern about the effects of the combustion of fossil fuels on the environment due to factors such as air pollution (from NOx, hydrocarbons and ozone) and global warming (from CO2). In recent years, research and development attention has focused on harvesting energy from natural environmental sources such as wind, flowing water, and the sun. Of the three, the sun appears to be the most widely useful energy source across the continental United States; most locales get enough sunshine to make solar energy feasible.
Accordingly, there are now available components that convert light energy into electrical energy. Such “photovoltaic cells” are often made from semiconductor-type materials such as doped silicon in either single crystalline, polycrystalline, or amorphous form. The use of photovoltaic cells on roofs is becoming increasingly common, especially as device performance has improved. They can be used to provide at least a significant fraction of the electrical energy needed for a building's overall function; or they can be used to power one or more particular devices, such as exterior lighting systems.
Photovoltaic roofing elements can be used to provide weather protection, like standard roofing elements, as well as photovoltaic power generation. Many such photovoltaic roofing elements take the form of a standard roofing element, such as a shingle or a tile (e.g., having a surface area of a few square feet), with one or more photovoltaic cells disposed thereon or integrated therewith. Photovoltaic roofing elements are generally difficult to install, however, as they must not only be physically connected to the roof in a manner that provides weather protection but also be electrically interconnected into a wiring system to be connected to the elements of a larger photovoltaic generation system (e.g., inverters, batteries and meters). Such installation often requires an electrical specialist to perform the electrical interconnections, which can be difficult to time appropriately with the physical installation of the photovoltaic roofing elements. Moreover, installation of many such individual roofing elements can be time consuming, as it requires electrical interconnection of many, many individual photovoltaic roofing elements. Time consuming installation is especially inconvenient when a workperson must perform it while up on an often steep roof.